Feb. 24, 1970 c. a. kiesling 3,497,760
LOGICAL EXPANSION CIRCUITRY FOR DISPLAY SYSTEMS
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Feb. 24, 1970 c. a. kiesling 3,497,760
LOGICAL EXPANSION CIRCUITRY FOR DISPLAY SYSTEMS
Filed June 10, 1968 6 Sheets-Sheet 4
Feb. 24, 1970 c. a. kiesling 3,497,760
LOGICAL EXPANSION CIRCUITRY FOR DISPLAY SYSTEMS
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Feb. 24 , 1970 c. a. kiesling 3,497,760
LOGICAL' EXPANSION CIRCUITRY FOR DISPLAY SYSTEMS
Filed June 10, 1968 6 Sheets-Sheet 6
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FROM PROCESSOR
United States Patent Office
3 , 497,760
Patented Feb. 24, 1970
1
3,497,760
LOGICAL EXPANSION CIRCUITRY FOR
DISPLAY SYSTEMS
Charles A. Riesling, Minneapolis, Minn., assignor to
Sperry Rand Corporation, New York, N.Y., a cor¬
poration of Delaware
Filed June 10, 1968, Ser. No. 735,617
Int. Cl. HOlj 29/70
U.S. Cl. 315—18 9 Claims
ABSTRACT OF THE DISCLOSURE
A display system having at least a first area for dis¬
playing characters and a second area for displaying both
vectors and characters, and having the ability to expand
both the characters and the vectors in the second area is
described. Circuitry for selecting an expanded mode for
at least a part, or sector, of the second area is also de¬
scribed. If the electron beam tends to move off-screen out
of the selected sector of the second area when in the ex¬
panded mode, circuitry is provided such that the digital
beam position is complemented and the beam is blanked
to allow the blanked beam to stay on-screen while mov¬
ing to the on-screen position where the beam is to re-enter
the selected sector for display. Override circuitry is also
described such that when the display system is in the ex¬
panded mode and a command is given to go from the se¬
lected expanded sector of the second area to a position in
the first area, the expansion circuitry is overriden to allow
normal operation of the display system while the beam is
in the first area. The display system has the capability
of displaying a series of characters, referred to as tabular
characters. Circuitry is described such that when the sys¬
tem is in the expanded mode a sequence of tubular char¬
acters beginning outside of the bounds of the expanded
sector are blanked and are continually blanked through¬
out the series of tabular characters. This eliminates the
trailing-end of fragmented tabular character series. The
display system also includes the capability of displaying
single characters, referred to as random characters. Cir¬
cuitry is also described such that when the display system
is in the expanded mode, the spacing between random
characters is expanded, but the spacing between tabular
characters is not expanded thereby retaining their read¬
ability.
BACKGROUND OF THE INVENTION
Field of the invention
This invention relates generally to visual display sys¬
tems utilizing a cathode ray with a two-dimensional dis¬
play of messages on the face of the display tube. Dis¬
play systems are becoming increasingly important in the
data processing industry for use in displaying alpha¬
numeric and graphic data. In order to display alpha¬
numeric characters, it is necessary to utilize a character
generator, and in order to display graphic data, it is neces¬
sary to utilize a vector generator. For many applications,
it is desirable that these vector and character display sys¬
tems include the ability to expand selected sectors of the
display area for greater ease of reading.
Description of the prior art
Prior art devices which have been provided systems for
expanding the data displayed on the screen lack the ability
to perform several important functions which are re¬
quired for full and proper use of the display systems.
Basically, in the prior art systems that provide for expand¬
ing the data displayed, the entire viewing screen is ex¬
panded. It has been found desirable that at least a portion
of the display screen be of a permanent display character-
2
istic even when another portion of the screen is to be
expanded. This feature of holding a portion of the screen
constant, that is unexpanded, while expanding another
portion of the screen is not to be found in the prior art.
This capability requires the ability to update the informa¬
tion in the non-expandable area even when the remainder
of the display area is in an expanded mode.
The prior art expanding display systems have an in¬
herent delay in the time that is required for the beam to
settle down once it has been driven to an off-screen posi¬
tion and is then brought back into a position in the ex¬
panded portion that is to be displayed. In the prior art,
when a particular sector of the display screen is expanded,
and the electron beam starts to move out of that sector,
the prior art circuits blank the electron beam and hold it
in that location. However, when the beam is to come back
into the expanded area, a time delay must be incorporated
in order to give the beam time to position and to settle
down and begin tracing (the displaying operation) in the
proper location. This time delay causes a reduced opera¬
tional rate.
The prior art display devices do not have provision for
expanding the spacing between particular characters in a
selected sector while not expanding the spacing between
other types of characters. This feature obtains significant
proportion in display systems that provide for displaying
both word-messages and character-messages in that by
expanding the spacing between letters of a word mes¬
sage, ambiguity can be raised in the mind of the viewer
as to whether the letter combination is in fact a word
message or whether the letters are in fact several discrete
letter-messages.
Closely associated with the foregoing problem of the
prior art is that the prior display devices make no provi¬
sion for correction of distortions or aberrations caused
when a sector is expanded such that only the trailing por¬
tion of a word or sentence is present at the edge of the
selected sector, with the leading portion of the message
being in another unselected sector. The prior art sys¬
tems make no provision for deleting these partial-message
displays at the edge of the sector and can lead to errone¬
ous interpretations of the messages displayed in the ex¬
panded sector.
SUMMARY
The display system of the present invention overcomes
and provides marked advantages over the several disad¬
vantages of the prior art display systems. Because of the
well-recognized need for certain data to be present on
the display screen even though a selected sector of the
remaining screen area is expanded, the present invention
provides circuitry for holding data for display on at least
a first area on the screen without expansion, and yet pro¬
vides means for updating that data even though a sector
of the second area is in the expanded mode. By utilizing
the circuits of this invention, this split operation, that is
a portion expanded and another portion unexpanded, can
be accomplished without disturbing the circuits that are
established for operating in the expanded mode.
This invention has also attended itself to the delay
problem inherent in the prior art when the electron beam
is tended to move out of an expanded sector to an off¬
screen position. Circuitry is included in this invention
such that when a selected sector is expanded, and the
beam tends to move out of the expanded sector to an
off-screen position, the beam is blanked and its position
is digitally calculated and complemented in a manner to
cause it to remain and move in a blanked on-screen path
that is the mirror image of the off-screen path that would
otherwise be followed. This operation results in a move¬
ment of the electron beam such that when the arithmetic
indicated that the electron beam should be tending to
5
10
15
20
25
30
35
40
45
50
55
60
65
70
3,497,760
3
move back into the expanded sector, the blanked electron
beam has traced the appropriate blanked on-screen path
and is at the proper position for entry back into the ex¬
panded sector without any time delay. Therefore, the
time that is necessary to quickly move the beam to the r
on-screen position from a held position of the prior art, 0
and the time necessary for allowing the electron beam
to settle down such that display can be resumed, has been
eliminated, and no time delay for this operation is re¬
quired. Accordingly, an enhanced operational rate is
realized.
The display system of the subject invention provides
for displaying individual or so-called random characters,
and grouped characters, such as for expressing word
messages, which are referred to as tabular characters. 15
Circuitry is provided such that the spacing between ran¬
dom characters in a selected sector can be expanded
thereby holding the relative relationship of the random
characters with regard to the other data that is also ex¬
panded. Holding this expanded relationship is important 20
for many display applications. The circuitry also pro¬
vides, however, for not expanding the spacing between
tabular characters. This is important for holding the
spacing in a word in order to clearly distinguish that
the tabular characters are in fact character-combination 25
messages which are to be viewed together, and are not
thereby confused with the random characters. Therefore,
when the selected sector is expanded, the circuitry pro¬
vides for expanded spacing only between random char¬
acters, while providing that the spacing between tabular 30
characters remain the same as that for tabular characters
that would appear on the screen in an unexpanded mode.
The subject invention has also provided means for
preventing distortion when a sector is expanded in which
the trailing end of a word or message is present in the 35
selected sector with the leading portion being present
in an unselected sector. The circuitry of this invention
operates under these conditions with tabular characters
such that the sequence of tabular characters, both within
and without the selected expansion sectors are blanked. 40
This provision is included since it is felt that the trailing
ends of messages would tend only to cause confusion to
the viewer. The system provides additional circuitry, how¬
ever, for displaying the remaining portions of tabular
characters that start in the selected sector, but which
extend to an adjacent unselected sector. In this opera- 4iJ>
tion, the tabular characters that would appear within
the selected sector also would appear in the expanded
mode, but those tabular characters which are not within
the selected expanded sector are blanked.
In view of the foregoing, it is a primary object of
this invention to provide an improved cathode ray tube
display system including means for expanding the scale
of the display for selected sectors for the display screen.
Yet another object of the invention is to provide a 55
cathode ray tube display system having means coupled
to the cathode ray tube for displaying data in the first
and second areas and having circuitry including an ex¬
pansion control circuit for expanding data in a selected
sector of only the second area on the screen. 60
Still another object of the invention is to provide a
cathode ray tube display system having circuitry coupled
to the cathode ray tube for displaying character data in
a first area of the screen and both character and vector
data in a second area of the screen, and having circuitry
including an expansion control circuit for expanding the
data in a selected sector of only the second area of the
screen without disturbing the data in the first area.
It is yet another object of the present invention to „
provide a display system having an expansion control 1
circuit which includes circuitry for selecting a particular
sector of an area to be expanded and producing a de¬
tection signal when the electron beam tends to move out
of the selected expanded sector and to provide means for 75
4
blanking the beam whenever the detection signal would
indicate an off-screen beam position.
It is still another object of this invention to provide
a display system having the cathode ray tube with first
and second areas on the viewing screen and having means
for receiving character signals representing that character
data that is to be displayed in the first area, with control
means coupled to the signal receiving means for over¬
riding the expansion control circuit thereby causing nor¬
mal display of the character signals received.
Yet a further object of the present invention is to pro¬
vide an arithmetic circuit which causes the complement
of the digital beam position to be used whenever the beam
tends to move out of its expanded selected sector, where¬
by the blanked beam will follow an on-screen path which
is the mirror image of the off-screen path that would
otherwise be followed.
It is still another object of this invention to provide
a display system having an expansion circuit wherein
tabular character groupings which begin beyond the
bounds of a selected expanded sector are blanked, and
the blanking continues throughout the entire tabular
character groupings even though the tabular characters
continue into the selected expanded sector.
Yet another object of this invention is to provide a
display system having an expansion circuit in which the
spacing between tabular characters remains constant and
is not expanded even though the tabular character group¬
ings exist in a sector that is selected for expansion.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other more detailed and specific
objectives will be disclosed in the course of the follow¬
ing specification, with reference being made to the ac¬
companying drawings in which:
FIGURE 1 is a diagrammatic representation of the
total display area on a cathode ray tube screen showing
upper and lower first areas for displaying characters and
a second central area for displaying either or both vec¬
tor and alpha-numeric character data;
FIGURE 2a is a view of the second area of the display
screen showing the available addressable message posi¬
tions on the display screen for that portion of the display
screen that is subject to being expanded;
FIGURE 2b is a table relating to FIGURE 2 a and
illustrates the expanded sector numbers together with
the associated areas that are expanded for the sector that
is selected;
FIGURE 3a illustrates the expandable portion of the
display screen in an unexpanded mode with a character¬
istic display shown thereon;
FIGURE 3b illustrates the results of expanding sector
5 of FIGURE 3 a and additionally illustrates the path the
blanked beam would attempt to follow if allowed to
pass off-screen out of the expanded sector;
FIGURE 3c illustrates the expanded sector 5 of FIG¬
URE 3a and illustrates the path the blanked beam will
follow when caused to stay within the expanded area;
FIGURE 4 is a general block diagram of the display
system of this invention; and
FIGURES 5a, 5b, and 5c, when arranged as shown in
FIGURE 5, collectively are a detailed block diagram
showing the novel circuit arrangements of the display
system.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
FIGURE 1 shows one arrangement of the cathode ray
display screen in which areas 12 are available for dis¬
playing data which cannot be presented in an expanded
mode. A second area 14, in this example the remainder
of the display screen, is capable of displaying data in the
normal or in the expanded mode. It should be under¬
stood that this display screen configuration is intended to
be illustrative only, and that the upper or lower fixed
area 12 could be eliminated, as well as being located at
3,497,760
5
some other place on the display screen. Additionally, the
dimensions of areas 12 and 14 can likewise be adjusted
to the larger or smaller as desired.
As mentioned above, one of the objects of this inven¬
tion is to provide an improved display system in which
data in a specific area or areas of the display screen can
be displayed in an unexpanded manner (normally) even
when a selected sector of the remainder of the display
area is displayed in an expanded mode. Provision is
made for altering, or so-called updating, of the data to be
displayed in this unexpandable area even though a se¬
lected sector in the second area is being operated in the
expanded mode. FIGURE 2 a shows the array of avail¬
able message display addresses for the area 14 of the
display screen. The addresses are illustrated along the
left edge and along the bottom edge in a binary code. It
can be seen that the X direction has a range of 0 through
111 2 and in the Y direction has a range of 0! through 111 2 .
This can be seen to be an 8 x 8 array or providing for 64
gross electron beam positions. This array is of course
illustrative only, and a display could have many more
co-ordinate positions, it being understood that this ex¬
ample provides a means for explaining how the system
works without confusing the understanding of the inven¬
tion. The numerals 1 through 9 appearing within the
circles in FIGURE 2 a identify the sector numbers that
are subject to being selected for expansion. For instance,
■referring to sector 1 it can be seen that it is bounded by
areas A, B, E and F. Next considering sector 2 it can be
seen that it is bounded by the areas B, C, F, and G. In
making the selection between sectors 1 and 2 it can be
seen that areas B and F are common to the two sectors
1 and 2. When considering sector 5, which is comprised
of areas F, G, J and K, it can be seen that there are areas
common to all of the other sectors. It can be seen, then,
that each sector that can be selected for expansion com¬
prises specific areas of the face of the display. In FIG¬
URE 2b is shown a table that identifies the specific areas
by letter that are included in the enumerated sectors. It
should be understood that the various sectors that can
be selected, as shown in FIGURE 2 a are expanded by
the circuitry of this invention to approximately fill the
area 14 illustrated in FIGURE 1.
It is old and well-known that to double the display
scale of a selected sector, it is merely necessary to dis¬
card the most significant bit in each of the X and Y
addresses, shift those addresses so as to multiply the sig¬
nificance of each of the remaining bits by 2, and suppress
the display of all characters having original addresses
falling outside the sector selected. It is also old and well-
known that to expand any of the overlapping sectors
such as 2, 5, 8 and 4, 5, 6 there is the additional step of
complementing the most significant bit in the expanded
X or Y address or both.
FIGURE 3 a shows the expandable area 14 with its
nine expandable sectors, having what might be called a
typical message shown thereon. It should be understood of
course that the numerals 1 through 9 would not appear
on the display, but are merely utilized for reference
purposes. The data message shown in FIGURE 3 a in¬
cludes a vector N, the words CAT, MIKE, and ABLE,
and the random characters G, K, and X. It will be noted
that the word MIKE begins in sector 4 and ends in sec¬
tor 5, while the word ABLE begins in sector 5 and ends
in sector 6. It will also be noted that the word CAT is
entirely within sector 5. These words are formed with
characters known as tabular characters, often referred
to as tab characters. It would be appropriate here to again
distinguish the tabular characters from the random
characters such as G, K, and X. The random characters
are those characters which may be positioned in any
specified location in the expandable area of this display
screen, and the tabular characters are those groupings of
characters that have a predetermined spacing. To dis¬
play the messages shown in FIGURE 3 a the beam posi-
6
tioning circuits are commanded to move the blanked beam
to a particular location in which the desired character or
line is to be displayed (painted) and then the beam is
specifically commanded to move to a new location where
the next specific character is displayed. However, when a
0 signal representing a tabular character is presented, the
blanked beam is moved to the predetermined starting posi¬
tion; the first tabular character is displayed; the blanked
beam is moved a fixed increment; the beam again stops;
and the next tabular character is displayed. This move¬
ment of a fixed increment and the displaying of the next
subsequent tabular character continues until all of the
tabular characters in the sequence have been displayed
and the control signal indicating that tabular characters
15 are being displayed has been removed. Accordingly,
tabular characters are placed side by side automatically
while random characters, if they are to be placed side
by side, must have a particular command associated with
each character to cause the blanked beam to be posi-
20 tioned to the desired random character location. Again
referring to FIGURE 3a, it will be seen that the words
CAT, MIKE, and ABLE are words comprised of tabular
characters while the characters G, K, and X are random
characters each of which must be located by a specific
25 command.
Turning now to a consideration of FIGURE 3b, which
shows sector 5 of FIGURE 3 a in its expanded state, it
will be noted that the random characters G, K, and X
have had their relative spacing expanded in the same pro-
30 portion as vector N. It should be noted, however, that the
word CAT, which is formed with tabular characters, has
not had the spacing between the characters expanded.
Accordingly, the same readability is present in the expand¬
ed mode as is present in the unexpanded mode. It can be
35 seen that the letters KE of the word MIKE are not
shown in the expanded view of sector 5 in FIGURE 3b.
This follows since the word MIKE began in sector 4
and only the data in sector 5 is shown. Accordingly, the
letters KE would form nonsensical information in the
4(> expanded sector and would tend to be confusing to the
viewer. It will be noted at the other edge of the expanded
sector, however, that the letters AB of the word ABEL
are shown in the expanded view of sector 5. It has been
determined that the starting portion of tabular character
messages may be useful even though not completely
u spelled out, and are therefore displayed in the expanded
sector. Of course it is clear that the letters LE which are
in sector 6 are not shown since they are not a portion of
the expanded sector 5.
FIGURE 3b also illustrates in dashed line form the
expanded portion of vector N that is in sector 6, and il¬
lustrates the path the blanked beam would tend to follow,
through the arithmetic manipulations of the addresses,
were it allowed to do so when in the expanded mode. It
rr can be seen that the beam tends to go off-screen. In the
prior art systems, when the beam reaches point 16 at
the right edge of the expanded sector shown in FIGURE
3b, it would be blanked and held in that position while
the arithmetic manipulation would continue to operate
gg as if the beam were going to follow path 18. When the
addressing would reach the point 20 where the beam
would be designated to re-enter the display area, it would
be necessary to provide time for the blanked beam to
move from point 16 to point 20 and to provide time for
g. the beam to settle down. At this point, then, the beam
would be unblanked and continue to move on the screen
to continue displaying the remainder of vector N. Of
course the same blanking and holding operation would
occur for segments 22 and 24 which reside in sectors 2
70 and 8 respectively, and are outside the area of expanded
sector 5. As mentioned above, this invention avoids the
necessity of the time delay that occurs in the prior art
whenever the beam is caused to be addressed to an off¬
screen position and is again subsequently caused to re-
75 enter the selected expanded sector. This time delay is
3,497,760
7
avoided by including circuitry in the addressing arithmetic
unit to cause the beam to be blanked when it tends to go
off-screen, and further to cause the arithmetic operation to
be complemented and the blanked beam allowed to move
on-screen continuously until it arrives at the point where
it would normally re-enter the selected expanded sector.
Directing attention to FIGURE 3c, this mode of opera¬
tion is illustrated. In this illustration, the dashed lines il¬
lustrate the paths that the blanked beam would follow
in tracing the on-screen paths for the portions of the
vector N that would normally be off-screen. In this regard,
it can be seen that the dashed path 18' is the image of
the path 18 illustrated in FIGURE 3 b for that portion of
the vector that resides in sector 6 . Similarly, path 22' is
the image path for that portion 22 of vector N that is
in sector 2, and path 24' is the image of that portion
of vector N that is in sector 8 . With the circuitry of this
invention using this method of operation, the system does
not require a delay when the beam arrives at point 20
since it will be immediately ready to be unblanked and
continue the display of the lower portion of vector N.
Turning now to a consideration of FIGURE 4 which
is a simplified and generalized block diagram of the
system which includes the subject invention, where there
is shown a processor 40 communicating with a cathode
ray display 42. The processor 40 can be any of several
commercially available processors and is utilized to pro¬
vide digital character generating signals on line 44, digital
X (or Y) vector component signals on line 46, and con¬
trol signals on line 48. The processor will normally in¬
clude data storage capacity and may include buffer stor¬
age for matching the rate of transfer to the display sys¬
tem. It will also have the capability to provide control
signals to the display. The various control lines for activat¬
ing and de-activating the display system that normally
are utilized between a processor and the display are not
shown since they do not tend to aid in the understanding
of the invention. The vector component signals that are
applied on line 46 may cause a vector to be displayed if
the electron beam is activated, or may cause the blanked
electron beam to move to a specified location on the face
of the display screen where either a vector can be started
or a character displayed. If a character is to be displayed,
the signals on line 46 will move the beam to the location
specified, and then the character signals on line 44 will
cause a character generator 50, which is coupled to the
display 42 by line 52, to generate the designated charac¬
ter. The character generator 50 can be selected from those
available commercially, and can be of the type disclosed
in commonly assigned patent application Ser. No. 436,174,
filed Mar. 1, 1965. The manner in which the vectors are
to be displayed has been disclosed in commonly assigned
copending application Ser. No. 701,432 filed Jan. 29, 1968.
In the last named copending application, a system is
described whereby vectors exceeding a certain size are
normalized and then treated as a series of segments to
form the total specified vector. Therefore, a normalizing
circuit 54 receives the vector component signals applied
on line 46 and inspects each of the X-Y vector compo¬
nents in input registers that are to be added to the present
beam position. The normalizing circuit is disclosed in the
last identified copending application and will not be de¬
scribed in detail, it being understood that the normalizing
circuit includes a portion for establishing a normalized
segment and a counter for establishing the number of
times the normalized segment is to be added to the present
beam position to achieve the desired vector. When the
normalizing circuit 54 examines the input component, the
normalizing circuit causes the component data to be shift¬
ed one or more places in storage registers until the vector
component is scaled to some value equal to or less than
a predetermined value for those component values that
exceed the predetermined value when tested. When the
scale value is reached, it is repeatedly added to the data
representing the present beam position in both the hori-
8
zontal and vertical co-ordinates until the vector starting
point is reached. Also included in the circuitry for cal¬
culating the beam position is an arithmetic circuit 56,
which includes an adder, and horizontal output register
r and digital-to-analog (D/A) converters 58. Since the op¬
eration of these circuits has been described in the above
identified copending application they will not again be de¬
scribed here. The horizontal output register and digital-to-
analog converters 58 provide signals on line 60 to the
horizontal deflection circuitry of the display system 42.
At this point it should be emphasized that the block dia¬
gram of FIGURE 4 illustrates the horizontal display con¬
trol only and that a similar arrangement of the control
circuits would be required for the vertical deflection con-
15 trol. The vertical deflection control is not shown, how¬
ever, since it would not add appreciably to the ease of
understanding of the invention.
It will be recalled from above, that the displaying of
tabular characters specified that there would be auto-
20 matically established spacing between the respective
tabular characters. To achieve this automatic spacing, a
character spacing circuit 62 is utilized. The character
spacing circuit will be described in more detail below.
Functionally, it operates under control of selected ones
25 of the input control flip-flops 64 to achieve the automatic
increment of spacing. The ones of the input control flip-
flops 64 that are relevant in the determination of the
character spacing are the character size flip-flop and the
flip-flop that determines whether a character or a vector
30 is being displayed. These control signals are transmitted
over line 66 to the character spacing circuit 62. The
character spacing circuit 62 operates to force over line
68 the increment of spacing to the arithmetic circuit 56.
The output gating circuit 70 operates on the value re-
35 ceived from the arithmetic circuit to finally alter the value
to be applied to the horizontal output register and D/A
converters 58. The operation of the output gating circuit
70 will be described in more detail below.
One of the primary objectives of this invention is to
’ provide a means for selecting a designated sector on the
face of the cathode ray display 42 for expansion to cover
the portion 14, as described above. In order to make the
selection, a sector selector 72 is coupled to ten switches,
which individually operate to apply an activating voltage
45 to the sector selector. Switches one through nine are
mutually exclusively operable for selecting the sector de¬
signated for expansion. A tenth switch labelled Normal is
selected whenever the display 42 is to be operated in the
normal, or nonexpanded mode. The result of selecting the
50 normal switch is to provide a signal on line 74 which is
directed to the expansion override circuitry 76 thereby
causing that circuitry to operate in the normal mode, and
to provide a Normal signal on line 77. The expansion
override circuitry 76 also receives a plurality of control
55 signals over line 79 from the input control flip-flops 64.
The physical arrangement of the ten switches, or push¬
buttons, is such that they are interlocked such that when¬
ever any one of switches one through nine is selected the
Normal switch is disconnected. By disconnecting the
60 Normal switch, the normal signals provided on 74 and
77 are removed, and it results in the expanded mode of
operation. When in the expand mode, the expansion over¬
ride circuit 76 provides an Expand signal on line 78
which is directed to the blanking circuit 80 and as a con-
65 trol signal to the character spacing circuit 62. Addition¬
ally, the Expand signal is one of the control signals ap¬
plied to AND circuit 82 which in turn provides one of
the control signals to the horizontal output register and
D/A converter 58. The output signal from AND 82 on
70 line 84 operates to shift the addressing data signals being
coupled to the horizontal output register a predetermined
amount for causing expansion.
The sector selector 72 also provides control signals over
line 86 to the blanking decoder 88 . The blanking decoder
75 receives signals over line 90 from the output gating cir-
3,497,760
9
cuits 70 and compares them with the signals received
on line 86 . The signals compared represent the two high¬
est ordered bit positions of the data available in the
output gating circuit 70. By comparing the signals from
the sector selector 72 on line 86 with the two highest
ordered bits in the output gating circuit 70, blanking de¬
coder 88 can produce signals on line 92 which indicate
when the present beam position, as represented by the
data in the output gating circuit 70, is out of the area
selected by the sector selector 72 for display. Therefore,
when a signal is present on line 92 and is directed to
blanking circuit 80, it indicates that the beam position is
out of the sector that has been selected to be expanded.
Accordingly, the signal on line 92 becomes a blanking sig¬
nal which prevents an intensity enable signal from beam
generated by the blanking circuit 80 on line 94 and oper¬
ates to blank the electron beam of display 42. It should
also be noted that the signal on line 92 from blanking
decoder 88 is couple to AND gate 82 along with the
Expand signal on line 78. These two signals represent that
the circuit is in the expand mode but that the arithmetic
data representing the present beam position is out of the
desired sector to be expanded and therefore a signal is
produced by AND gate 82 on line 84 to cause the signals
being received to be complemented and results in the
blanked beam being moved within the sector as shown
and discussed with relation to FIGURE 3c. Thus, when
in the expanded mode, if the electron beam tends to move
off-screen out of the selected expanded sector of the area
of the display 42, the digital beam position being coupled
to the horizontal output register 58 is complemented and
the beam is blanked by the signal on line 92, thereby
allowing the blanked beam to stay on-screen while mov¬
ing to the on-screen position for the beam would have re¬
entered the selector sector had it continued in an off¬
screen path.
Turning now to a consideration of the display system
when it is selected in the expanded mode and a command
is given to go from the selected expanded sector to a
position in one of the areas 12 where characters will be
displayed, it can be seen that processor 40 will produce
signals on line 48 which will set the proper input control
flip-flops 64. The operation of the appropriate input con¬
trol flip-flops will result in signals on line 78 to the expan¬
sion override circuit 76 which will produce output signals
on line 77 to override the Expand signal on line 78 and
cause the Normal output signal to appear. As will be de¬
scribed in more detail below, one of the input control
flip-flops will produce a signal on line 96 which is directed
to the arithmetic circuit 56 and indicates that the electron
beam is to be positioned. The signal on line 96 enables
the addressing data provided on line 46 to pass on line
46' directly to the arithmetic circuit 56, thereby bypass¬
ing the normalizing circuit 54 and the character spacing
circuit 62. The addressing data presented on line 46 at
this time will be a total address with regard to the refer¬
ence side of the display and will cause the blanked elec¬
tron beam to be forced to the specified starting position.
This addressing data which represents the position in the
area 12 of the display 42 to which the beam is to move is
coupled directly through the output gating circuit 70 due
to the gating signal of the normal operation received on
line 77. Having thus forced the position of the blanked
beam, the display 42 is in a condition to either display a
series of tabular characters or to display a random char¬
acter. Since the display is going to be in the area 12 of
the display 42, the next control signal to be received on
line 48 sets the appropriate input control flip-flop 64 such
that a signal on line 66 will indicate that characters are
to be displayed. This Character signal on line 66 and the
Normal signal on line 77, both of which are coupled to
the character spacing circuit 62, cause a set of digital data
values representing the spacing between characters to be
coupled to the arithmetic circuit 56 and added to the
present beam position. The character signals will then be
10
provided on line 44 to the character generator 50 which
in turn will display the appropriate character. If tabular
characters are being displayed, this space and display
sequence will be repeated until such time as the control
signal is given that the tabular character sequence has
been completed. The foregoing has been a general discus¬
sion of the operation of this improved display system. A
consideration of the detailed logic arrangement of FIG¬
URES 5a, 5b and 5c will indicate the specific operation
jO of the elements described generally above.
Having considered the broad functional operations of
the invention, the following discussion will be with re¬
gard to the detailed logic illustrated in FIGURE 5a,
FIGURE 5b, and FIGURE 5c, when arranged as shown
15 in FIGURE 5. These figures collectively are a detailed
logic block diagram of the portions of the improved dis¬
play system that provide the functions of this invention.
In these figures, elements that have been previously de¬
scribed are provided with the same reference numerals as
20 utilized previously. Lines in FIGURE 4 that are com¬
prised of more than one conductor, are shown cabled
in these figures with the individual conductors being pro¬
vided with a dash numerical designation appended to the
cabling numeral. The logic circuits illustrated in these
25 drawings are of a conventional type readily available in
the commercial marketplace. These logic circuits include
AND circuits, which have the logical function of pro¬
viding an output 1 signal when all input signals are 1 .
In the event that any input signal is other than 1, the out-
30 put of the AND circuit will be 0. The OR circuit operates
such that any input terminal receiving a 1 signal will re¬
sult in the output terminal providing a 1 signal. Only for
those situations where all input terminals receive 0 signals
will the output terminal provide a 0. The inverter circuits
3o are referred to as I and operate to invert the function of
the input signal such that if a 1 signal is received at the
input, a 0 signal is provided at the output, and a 0 at the
input results in a 1 at the output. The flip-flop circuits
(F/F) are bistable flip-flop circuits and are of an opera-
u tion such that it requires a 1 input to the set terminal(s)
to provide a 1 at the 1 output terminal. When the flip-flop
is providing a 1 at the 1 output terminal, it will be pro¬
viding a 0 at the 0 output terminal. When a 1 signal is
received at the clear input terminal (C), the flip-flop will
45 provide a 1 at the 0 output terminal and a 0 at the 1 out¬
put terminal. The circuit operation is such that when the
flip-flop has been set by providing a 1 at the S input ter¬
minal, a subsequent 0 at the S input terminal will be in¬
effective to alter the state of the flip-flop. In order to clear
50 the flip-flop it is necessary to subsequently apply a 1 to
the C input terminal. The Exclusive-OR circuit (EX-OR)
is a circuit that provides a 1 output signal if, and only
if, only one of the two input terminals is receiving a 1
signal. In the event the input terminals each receive 0
55 signals or each receive 1 signals, the output of the Ex¬
clusive-OR will be a 0 signal. The registers are comprised
of a plurality of parallelly arranged flip-flop circuits. It
should be understood that the arbitrary reference to l’s
and 0 ’s could equally as well be reversed in all cases
60 such that the logic reference is 0 ’s rather than referring to
l’s. It should also be understood that the voltage levels
representing l’s and 0 ’s can be arbitrarily defined, it being
necessary only to accommodate the logic circuits to per¬
form those functions specified above. It should be fur-
65 ther understood that the logic functions can be accom¬
plished by well-known diode and transistor logic circuits
of the discrete component type, or can be grouped such
that the same logical functions are provided by more com¬
plex logic circuits. While the logic functions are shown
70 as separate entities, some of the elements can be com¬
bined physically.
From above it will be recalled that the processor pro¬
vides a sequence of control signals and addressing data
for establishing what operation is to be performed and
75 where the operation is to be performed in the display 42.
3,497,760
11
Additionally, the processor provides the data signals that
specify the type of character to be displayed as well as
the data that specifies the vectors that may be generated.
The characters that are to be generated are supplied over
line 44 to the character generator 50 which in turn pro- g
vides the generation signals over line 52 to the display
42. When characters are to be displayed, it is necessary
that several of the input control flip-flops, shown enclosed
in dashed block 64, be set. Flip-flop F/F2, referred to
as the random or tab flip-flop, must be set or cleared
depending upon whether it is desired to display random
or tabular characters. If random characters are to be dis¬
played, a 1 signal must be applied on line 48-2, thereby
establishing a 1 at the R output terminal and a 0 at the
T output terminal. If tabular characters are to be dis- 15
played, it is necessary that a 0 be applied on line 48-2
such that, when inverted by I 64-2, it will provide a 1
at the C input terminal thereby establishing a 1 at the T
output terminal and a 0 at the R output terminal. It is
necessary also to display characters that a 0 be applied 20
on line 48-3 such that I 64-3 provides a 1 signal to the
C input terminal of F/F3, thereby providing a 1 at the
C outpt terminal and a 0 at the V output terminal. It is
necessary to select also whether the character is going
to be displayed in the normal areas 12 or in the expanda- 25
ble area 14. For ease of reference, the expandable area 14
is referred to as the vector area. Accordingly, if the char¬
acter is to be displayed in area 14 it is necessary to apply a
1 signal on line 84-4 to the S input terminal of F/F4,
thereby providing a 1 signal on the ON output terminal 30
and a 0 on the OFF output terminal If the character
is to be displayed in the fixed areas 12 , it is necessary to
apply a 0 on line 48-4 such that I 64-4 provides a 1 to
the C input terminal, thereby providing a 1 on the OFF
output terminal and 0 on the ON output terminal. For 35
the latter case, it is necessary to select between the top or
the bottom area 12. In order to make this selection, a 1
signal on line 48-5 will result in F/F5 providing a 1 on
the T output terminal and a 0 on the B output terminal.
Alternatively, if it is desired to display the character at 40
the bottom portion of the display 42, a 0 signal on line
48-5 will result in I 64-5 providing a 1 signal to the C
input terminal which will result in a 1 at the B output
terminal and a 0 at the T output terminal. It is necessary
also for displaying a character that F/F 6 be set. Accord- 45
ingly, it is necessary to apply a 1 signal on line 48-6 to
the S input terminal, thereby providing a 1 at the P out¬
put terminal and a 0 at the P output terminal. In the
event that a 0 is applied to line 48-6, I 64-6 will result
in a 1 being applied to the C input terminal whereby a 50
1 will appear at the P output terminal and a 0 a the P
output terminal. This latter operation will result in blank¬
ing the beam. Finally, in order to display a character it
is necessary to select between large and small characters.
With a 1 applied to line 48-7, F/F7 will have a 1 signal 55
at its 1 output terminal, thereby indicating a small char¬
acter and will have a 0 at its 0 output terminal. The ap¬
plication of a 0 to line 48-7 will result in I 64-7 applying
a 1 to the C input terminal, thereby providing a 1 at the
0 output terminal and indicating that a large character is 60
to be displayed. By making the appropriate selections of
those alternatives just described, a character of a prede¬
termined small or large size will be displayed in the top
or bottom area 12 or in the vector area 14 and the char¬
acter will be either a random character or a tabular char- 65
acter. As a result of setting these control flip-flops, the
remainder of the circuitry will be controlled automatically.
In determining the character spacing, which is per¬
formed automatically for tabular characters, attention is
directed to the character spacing circuitry shown enclosed 70
in dashed block 62. At the outset, let it be assumed that
the Normal button selection is made such that a signal
on line 74 directed to the expansion override circuit,
shown enclosed within dashed block 76, results in a
Normal output signal on line 77. This can readily be seen 75
12
in that OR 76-1 will provide the 1 output signal directly
on line 77. Further, I 76-2 will invert the 1 signal and
result in a 0 on the Expand line 78. For the Normal
selection it can be seen that AND 62-1 and AND 62-2
in the character spacing circuit 62 will be activated. Also,
having made the selection of the character output of
flip-flop F/F3, it can be seen that the output from the
normalizing circuit 54 will be blocked. This follows since
I 62-3, I 62-4, and I 62-5 will all provide 0 output sig¬
nals such that AND 62-6, AND 62-7, and AND 62-8
will be disabled. At this point it should be pointed out that
when the vector operation is selected such that a 0 is pro¬
vided on the character line 66 , the circuits I 62-3, I 62-4,
and I 62-5 will provide enable signals to their respective
AND circuits, thereby passing the output of the normal¬
izing circuit 54 directly through to the register 62-10.
However, for the display of characters, the normalizing
circuit 54 is blocked and a selected increment for char¬
acter spacing is provided to register 62-10. The character
spacing is based on the selection of whether the character
to be displayed is a small or a large character. Obviously,
the large characters require more space on the display,
hence will require a larger automatic spacing to accom¬
modate successive larger characters. If it is assumed at
the outset that a large character is to be displayed, a 1
signal will be provided from F/F7 on line 66-1 to AND
62-11. With the character signal provided on line 66 ,
AND 62-11 will be enabled and will provide a 1 signal to
AND 62-2 and AND 62-12. It will be recalled that for
this example the Normal mode has been selected. There¬
fore, AND 62-2 is enabled and will provide a 1 signal to
OR 62-13. This will result in a 1 being forced to the ith
position of register 62-10. It can be seen that this will
be a stage that provides a known increment over line 68
to the adder 56-1. It will be noted also that AND 62-12
is not activated since the Expand signal on line 78 is
absent. Next assume that the size controlling flip-flop
F/F7 has been so set to designated that the small char¬
acter is to be displayed, such that a 1 appears on line
66 - 2 , and together with the 1 signal on line 66 will acti¬
vate AND 62-14. Since AND 62-1 has the Normal signal
applied thereto, when coupled to the 1 signal provided
from AND 62-14, there will be a 1 signal applied to OR
62-15. This will result in the ith—1 stage of register
62-10 being set. It can be seen that the value that will
be passed to the adder 56-1 will provide the lesser spac¬
ing than that provided if the ith stage is set, thereby ac¬
commodating the small character spacing. The 1 output
signal from AND 62-14 is also applied to AND 62-16,
but since the Expand input signal is 0 there will be a 0
ouput signal to OR 62-17. It can be seen that this ar¬
rangement provides for a spacing between small and
large characters of a power of two. If some spacing other
than a power of two is desired, the appropriate translation
circuitry can be provided for accommodating the setting
of desired combination of stages in the register 62-10 for
application to the adder 56-1.
Next let is be assumed that one of the sector selection
pushbuttons has been activated for expanding a desired
sector, thereby de-activating the signal on line 74. By de¬
activating the line 74, OR 76-1 in the expansion override
circuit 76 will result in a 0 being applied to I 76-2 and
will result in a 1 (Expand) signal on line 78. Again
referring to the character spacing circuit 62, it can be seen
that the Expand signal on line 68 will result in AND
62-16 and AND 62-12 being enabled. Then depending
upon the selection of large or small characters, as deter¬
mined by the signals on line 66-1 and 66-2, either AND
62-16 or AND 62-12 will provide the spacing constant
for register 2-10. For the small character, AND 62-16
will be activated thereby passing a 1 signal through OR
62-17 and setting the ;th—2 stage. For the large character,
AND 62-12 will be activated, thereby passing a 1 signal
through OR 62-15 to the ith—1 stage of the 62-10 reg¬
ister. In the expanded mode, the spacing selected as shown
3,497,760
13
will be compensated by the path selectd in th output gating
circuit, shown enclosed in dashed block 70. This will be
described in more detail below. Having determined the
value of the increment that is to be automatically added
for spacing the tabular characters, and having provided
the increment value on line 68 to adder 56-1, which re¬
ceives as its other input the value held in the horizontal
storage register 56-2 via line 56-3, it is necessary to deter¬
mine the requirements for enabling AND 56-4. Returning
to the input control flip-flops, it will be recalled that to 10
display a character it is necessary for F/F3 to provide a
1 on the C output terminal. This signal is applied to AND
76-3 in the expansion override circuit. In order to display
tabular characters it is necessary that F/F2 provide a 1
on the T output terminal. Accordingly, a 0 signal will be 15
applied at the R output terminal to AND 76-3. This will
result in a 0 being applied on line 76-4 to OR 76-5.
Also, in order to display a character it is necessary that
the paint circuit F/F 6 have a 1 at the P output terminal.
Accordingly, the P output terminal will apply a 0 to AND 20
76-6, thereby applying a 0 to OR 76-5. With both input
terminals receiving a 0, OR 76-5 will provide a 0 output
signal on line 96 to the arithmetic circuit 56. This 0
signal will be applied to I 56-5 where it will be inverted
to a 1 signal thereby enabling AND 56-4 and allowing 25
the result that is provided by the adder to be gated to the
horizontal storage register 56-2. The 0 signal applied to
AND 56-6 will inhibit the transfer of the data provided
on line 46' to the horizontal storage register 56-2. There¬
fore, having selected the appropriate increment to be 30
added to the previously existing position of the beam, as
determined by the horizontal storage register, and having
gated this combined value to the horizontal storage
register, the output gating circuitry 70 can be considered
for establishing the ultimate position that the beam will 35
be moved to for painting a character.
Again assuming that the normal mode has been selected
such that a 1 signal is present on line 77, and that the
normal increments have been selected in the character
spacing circuit 62, it can be seen that the circuits AND 40
70-1, AND 70-2, AND 70-3, and AND 70-4 are en¬
abled. These circuits receive input signals from respec¬
tively associated stages of the horizontal storage register
56-2. Accordingly, by activating these AND circuits
the value stored in the horizontal storage register is ^
passed through the respective AND circuits ultimately
to the horizontal output register 58-1. It can be seen
that AND 70-1 provides its signal directly to the as¬
sociated stage of the horizontal output register; AND
70-2 provides its output signal to OR 70-5; AND 70-3 -q
provides its output signal to OR 70-6; and AND 70-4
provides its output signal to OR 70-7. From this opera¬
tion it can be seen that the increment selected between
tabular characters and provided in the character spacing
circuit 62 has been added to the previously existing beam gg
position and gated directly to the horizontal output
register 58-1.
Next assume that the expand mode of operation has
been selected such that a 1 signal is provided on line
78. The 1 signal on line 78 operates to activate AND gg
70-8, AND 70-9, AND 70-10, and AND 70-11. For
reasons that will become more clear when the vector
generation is explained, it will be seen that the gating for
the expand mode results in the output gating circuit
of the value being shifted one place thereby multiplying gg
the value by 2. Referring again to the character spacing
circuit operation, it will be recalled that for the expand
mode the increment was in fact divided by a factor of 2 .
Accordingly, when the two operations are combined
for tabular characters in the expand mode it can be 70
seen that the result is that the spacing stays the same
as that for the normal mode. The shifting is accom¬
plished by the lowest stage of the horizontal storage
register 56-2 being directed to AND 70-8, which is
enabled by the Expand signal such that the signal is 75
14
passed through to OR 70-5 to the next higher ordered
stage in the horizontal output register 58-1. This same
operation proceeds as a shift for all stages of the hori¬
zontal storage register except the highest ordered stage,
which is discarded for the expand mode. The value of
the highest ordered stage that will result in the horizontal
output register 58-1 will be determined by the value
of the two highest ordered stages in the horizontal
storage register 56-2. It can be seen that the highest
ordered stage is directed over cable 90 on conductor
90-1 to the blanking decoding circuit 88 . Further, the
next to the highest ordered stage is directed over cable
90 on conductor 90-2 to the blanking decoding circuit.
The value of the highest ordered stage will depend upon
the sector selected. For the horizontal circuitry, the
selection of sectors 2, 5, or 8 will result in a 1 output
signal over line 86-1 which will result in a 1 signal
on line 86-2 which is provided as an enable signal to
AND 70-11. It can be seen that the next to the highest
ordered stage is coupled as an input to I 70-12. Ac¬
cordingly, in the expand mode for sectors 2, 5 or 8 , in
the horizontal selection, the complement of the next
to the highest ordered stage in the horizontal storage
register will be applied to OR 70-7 and will reside
ultimately in the highest ordered stage of the horizontal
output register 58-1. This 1 signal resulting on line 86-1
will also be applied to I 88-1 in the blanking decoding
circuit such that a 0 is provided on line 92-1 to AND
70-10, thereby inhibiting the transfer of the true value
through AND 70-10. Alternatively, if any sector other
than sectors 2, 5 or 8 are selected, there will be a 0 on
line 86-1, such that a 0 is applied on line 86-2. This
will result in inhibiting AND 70-11. The 0 signal will
also be applied to I 88 - 1 , which in turn will provide a
1 on line 92-1 to AND 70-10. This will enable the
true value of the next to the highest ordered stage in
the horizontal storage register 56-2 to be passed through
OR 70-7 to the highest ordered stage of 58-1.
When the operation is selected to be in the expanded
mode, it is necessary to select one of the sector selec¬
tion pushbuttons for the desired sector. These push¬
buttons for a nine sector array are utilized to control
three OR circuits which comprise the sector selector
shown enclosed within dashed block 72 for the horizontal
selection. Sector selections 1, 4 and 7 are directed to
OR 72-1; sector selections 2, 5 and 8 are directed to
OR 72-2; and selections 3, 6 and 9 are directed to OR
72-3. It should be noted that various combinations of
these same selections are directed to the vertical con¬
trols. It is the function of the sector selector 72 for the
horizontal, and the corresponding sector selector (not
shown) for the vertical control, to establish which of
the segments must be blanked during the displaying
operation. The output terminals from the sector selector
72 are directed to the blanking decoding circuit shown
enclosed in dashed block 88 . These signals in combina¬
tion with the signals derived from the two highest ordered
digits of the horizontal storage register 56-2 are utilized
for determining when the electron beam is to be in the
active or in the blanked condition. The selection of sec¬
tors 1, 4 or 7 is directed over line 86-4 to AND 88-2.
The result of the selection of sectors 2, 5 or 8 is directed
over line 86-1 to AND 88-3; and the result of the selec¬
tion of sectors 3, 6 or 9 is directed over line 86-3 to
AND 88-4. The output signals from AND 88-2, AND
88-3, and 88-4 are directed to OR 88-5, which in
turn provide an output on line 92-2 as one of the input
signals to AND 82. The output of OR 88-5 is also di¬
rected on line 92-2' to OR 80-1 in the blanking circuit,
shown enclosed in dashed block 80. Any input condition
that results in a 1 signal on line 92-2 results in the
beam being blanked.
It can be seen that for each of the three sets of sectors
that a different combination of the higher ordered two
digits of the horizontal storage register 56-2 is utilized
3,497,760
15
to control the blanking operation. For sections 1, 4 and 7,
the addressing is such that when the highest ordered digit
is a 1, as indicated on line 90-1, AND 88-2 provides a
1 output to OR 88-5. The highest ordered digit is also
directed to I 88-6 where it is inverted and directed as an
input over line 88-7 to AND 88-4. Therefore, for sectors
3, 6 or 9 when the highest ordered digit is 0 it will be in¬
verted to a 1 signal by I 88-6, and will complete the
input requirements for AND 88-4 to provide a 1 OR
88-5. Finally, it is necessary to consider the highest or¬
dered and the next highest ordered digits in the horizontal
storage register in establishing which of the addressing
combinations must be blanked for sectors 2, 5 or 8. The
highest ordered digit is directed Exclusive-OR 88-8, to¬
gether with the next highest ordered digit, which is car¬
ried over line 90-2. As indicated above, the function of
the Exclusive-OR is to provide a 1 at the output ter¬
minal if, and only if, the input signals are dissimilar.
In the event that the input signals are alike, whether they
both be 0 or 1, the output signal will be 0. The output
from the Exclusive-OR is directed on line 88-9 as an in¬
put to AND 88-3. Therefore, when the higher ordered
two digits are dissimilar and either sectors 2, 5 or 8 is
selected, the input signals to AND 88-3 will be such that
a 1 signal is provided to OR 88-5. If, then, the system is
in the expand mode such that AND 82 is receiving a 1
signal on line 78-1, and any of the input conditions just
described are present so that a 1 signal is present on line
92-2, AND 82 will provide a 1 signal on line 84. This
will control the operation of the horizontal output
register 58-1. It will be recalled from above, that when
the beam position is directed to tend to move to an off¬
screen position, the system has been designed such that
the beam will be blanked and the complement value will
be utilized to move the blanked beam in an image pat¬
tern on-screen. In order to accomplish this, with the ad¬
vent of a 1 signal on line 84, the 1 signal is applied on
line 84-1 to enable the transmission of the complement
of the value stored in the horizontal output register 58-1
to the D/A conversion circuitry for driving the beam on¬
screen. The signal received on line 84 is also directed to
I 58-2. For those situations when the beam is found to be
on-screen, AND 82 will provide a 0 on line 84. This 0
will be inverted by I 58-2 and result in a 1 signal on
line 58-3. This will enable the transmission of the normal,
or true value, of the address stored in the horizontal out¬
put register 58-1. In this manner it can be seen that one
of the objectives of the invention of retaining the beam
on-screen for all operations has been achieved.
Turning now to a consideration of the expansion over¬
ride circuitry shown enclosed within dashed block 76, it
can be seen that all of the input control flip-flops 64 with
the exception of the character size. F/F7, are utilized
in the control operations of the expansion override cir¬
cuitry. As described previously, AND 76-3 is enabled
on the condition that a random character is selected by
F/F2 and a character selection is made in F/F3. The re¬
sult of this selection is to provide a 1 signal on line 76-7
as one input to AND 76-8, and to provide an input on
line 76-4 to OR 76-5. AND 76-8 is one of the control
circuits utilized in establishing that the electron beam
should be enabled. When character generator 50 is op¬
erative to paint a character, it also provides intensity con¬
trol signals on lines 50-1. These control signals are di¬
rected to OR 76-9 where it is directed to AND 76-8
and AND 76-10. The final condition for enabling AND
76-8 is that it be determined that the beam has been posi¬
tioned to the desired location as indicated by F/Fl being
set such that a 1 signal is provided at the END output
terminal on line 79-1. This signal is directed to the proc¬
essor to tell the processor that the display system is
ready to receive further input commands, and is also di¬
rected on line 76-11 as an input to AND 76-8, thereby
indicating that a random character can be displayed. The
1 signal derived on line 100 is directed to OR 80-2 in
16
the blanking circuit. The result of a 1 being directed
to OR 80-2 is to provide a 1 to AND 80-3. At the same
time, the paint flip-flop F/F6 has been set such that the
P output terminal is at the 0 level. Accordingly, AND
g 76-6 provides a 0 output on line 102, which is directed
° to OR 80-4. The 0 signal to OR 80-4, if all other inputs
are 0, results in a 0 signal being directed to I 80-5 where
it will be inverted to provide a 1 signal on line 80-6 to
AND 80-3. This condition will result in AND 80-3 being
10 activated to provide a 1 on line 94, thereby enabling the
electron beam. Should the condition be set that F/F6 is
providing a 1 output signal on the P output terminal
and the flip-flop F/F3 is set such that a 1 is being pro¬
vided on the V output terminal, AND 76-6 will provide
15 a 1 on line 102 as an input to OR 80-4. This 1 will re¬
sult in a 0 being provided by I 80-5 to line 80-6. This
will disable AND 80-3 and cause the intensity enable to
be removed, thereby blanking the electron beam. AND
76-12 requires that F/F6 be set such that a 1 signal is
20 provided at the P output terminal, that F/F3 be set such
that a 1 is provided at the V output terminal, and that
the beam flip-flop F/Fl be cleared such that a 1 is pro¬
vided at the END output terminal, in order to provide
a 1 output signal on line 104 to OR 80-2, thereby blank-
25 jng the beam. AND 76-13 and AND 76-14 provide the
control for the override for tab characters to be written
in the top or bottom portion of the display 42 even
though the display is in the expanded mode. AND 76-13
is activated by a signal from F/F5 indicating that the
30 selection is for the bottom of the screen; the selection
from F/F3 indicating that a character is to be painted;
the selection from F/F2 that the character is to be a tab
character; and the selection from F/F4 that the display
is to be off the vector area 14. When these conditions
35 exist, all of the input signals to AND 76-13 will be 1
and the output signal on line 76-15 will be a 1. This
signal is directed to OR 76-1 where it will be directed
as an output over line 77 as a Normal signal indicating
that there is a normal mode. The same signal from AND
40 76-13 is also provided on line 76-16 to OR 76-17. A 1
signal directed to OR 76-17 will be provided as one of
the input signals on line 76-18 to AND 76-10. A 1 at
this point will complete the selection such that AND 76-
10 will provide a 1 signal on line 106 to OR 80-2, there-
45 by providing one of the means of activating AND 80-3
for providing an intensity enable on line 94. This will
allow the tabular character to be painted. Returning to
a consideration of AND 76-14 it will be seen that it will
be activated under tthe same conditions as AND 76-13,
50 with the exception that F/F5 will be in the Set condition,
whereby a 1 will be present at the T output terminal
indicating that the display is to be at the top portion
of the display screen. When the other input conditions
are met, AND 76-14 will provide 1 output signal on line
55 line 76-19 to OR 76-1 where it will again cause a Nor¬
mal signal to be impressed on line 77 indicating that
there is a normal mode.
Additionally, a 1 signal will be provided on line 76-20
as an input to OR 76-17. Again, AND 76-10 will be
60 activated and will provide a 1 signal on line 106 for en¬
abling the intensity control. It can be seen, therefore,
that another of the objectives of the invention has been
fully described in that the character display in the portions
12 of the screen can proceed in a normal manner, that
65 is unexpanded, even though the expanded mode for area
14 has been selected. This operation is carried forward
without disturbing the circuitry that will permit the ex¬
panded operation to continue once the characters have
been displayed in the areas 12.
70 Turning next to the consideration of a blanking cir¬
cuitry, shown enclosed in dashed block 80, there has
already been discussed some of the operation that per¬
mits the enabling of the intensity control for unblanking
the electron beam. There are several ways in which the
75 electron beam can be blanked. As previously described,
the output signal from. OR 88-5 in the blanking de¬
coder circuitry 88 is directed on line 92-2' to OR 80-1.
When this signal is a 1, it is provided on line 80-7 as an
input to AND 80-8 and on line 80-9 as an input to AND
80-10. When the display is in the expanded mode, as
provided by a 1 signal on line 78, there will be a signal
applied on line 78-2 to AND 80-8 and on line 78-3
to AND 80-10. These 1 signals provided to AND 80-10
will result in a 1 being directed over line 80-11 to OR
80-4. The 1 output signal from OR 80-4 will be inverted
by I 80-5, and will result in AND 80-3 being disabled;
hence, will result in the beam being blanked. Returning
briefly to the expansion override circuitry 76, it can be
seen that AND 76-21 will provide a 1 output when F/F4
is set, thereby indicating that the display is on area 14;
F/F3 is cleared, thereby indicating that a character is
being painted; and F/F2 is cleared, thereby indicating
that tab characters are to be painted. Under this condi¬
tion, AND 76-21 will provide a 1 signal to OR 76-17,
thereby resulting in a 1 signal on line 106. It will also
provide a 1 signal on line 108 to AND 80-8, thereby
completing the requirements to provide a 1 signal to the
Set input terminal of the blanking flip-flop 80-12. The
setting of blanking flip-flop 80-12 will result in a 1 signal
on line 80-13 being provided as an input to OR 80-4.
Again, the 1 input to I 80-5 will result in a 0 on line
80-6 disabling AND 80-3 and blanking the beam. The
signal on line 108 is also applied to I 80-14. Since a 1
signal is received, a 0 will be provided to the C input
terminal, and will have no effect on the blanking flip-
flop. At such time as any of the control flip-flops F/F4,
F/F3, or F/F2 are altered, the control AND 76-21 will
provide a 0 signal on line 108. Then, I 80-14 will provide
a 1 to the Clear input terminal of the blanking flip-flop
80-12, and will result in a 0 being applied on line 80-13
thereby permitting other control signals to enable the
electron beam intensity. It is this feature that controls
the blanking of tab characers that are started outside of
a selected sector and continues the blanking even though
the tab characters extend into the selected sector. The
control of the blanking flip-flop 80-12 is such as to hold
the beam blanked until such time as the sequence of tab
characters has been terminated.
Having considered the displaying of various kinds of
characters and the various operational selections that can
be made with regard to characters, it is now appropriate
to consider some of the applications that are available
in this invention for the displaying of vector quantities.
One such possibility is the use of the vector control for
positioning a blanked beam for either starting a vector,
or starting a series of tabular characters, or for display¬
ing a random character. For this operation, the input
control flip-flops F/F 6 and F/F3 are to be considered.
The paint flip-flop must be in a condition such that Jt
is cleared, thereby providing a 1 on output terminal P.
This indicates that the beam is to be blanked. Secondly,
F/F3 must be set such that a 1 is provided at the V out¬
put terminal, thereby indicating that a vector operation
is to be made. These two signals are directed to AND
76-6 which in turn provides a 1 signal to OR 76-5. The 1
to OR 76-5 puts a I on line 96, where it is directed to
AND 56-6. The other input signals to AND 56-6 are
the input control signals received on line 46'. The en¬
abling of AND 56-6 results in the input signals bypassing
the normalizing circuit and the character spacing circuits
and being applied directly to the horizontal storage reg¬
ister 56-2. For the gross movement of this operation, the
input command is an address that references the beam
position with regard to a reference position. This value
is forced to the horizontal storage register and from
there is directed to the output gating circuit where it
controls the operation of the horizontal output register
and causes the beam to be moved to the position specified.
It will be recalled also that AND 76-6 provides a signal
on line 102 such that when it is a 1 signal, it will provide
a control of OR 80-4 to cause a 1 to be applied to I
80-5. In turn, I 80-5 will invert the signal to a 0 and dis¬
able the intensity enable, thereby blanking the beam.
As previously indicated, a vector operation results in
the use of the normalizing circuit when the vector ex¬
ceeds a predetermined value. When the vector signals
are normalized, a counter 110 is set depending upon the
number of shifted positions that are accommodated by
the normalizing operation. This counter then operates
to count down for the number of segments that must
be gated into the adder 56-1. While the counter is
counting, 0 signals are applied to the set input terminal
of F/Fl and I 64-1 operates to hold F/Fl in the cleared
state. When the counter has counted through all of the
15 segments, a 1 signal is applied to the Set input terminal
and the flip-flop is switched to a set condition, indicat¬
ing that the beam is at the end thereof. The flip-flop F/F3
operates to control the operation for the vector quantity.
When this flip-flop is Set such that a 1 signal is applied
20 at the V output terminal thereof, a 0 is provided at the C
output terminal, as previously described. This 0 output
signal is provided over line 66 as an input to the I 62-3,
I 62-4, and I 62-5. These 0 signals are inverted and
function to enable AND 62-6, AND 62-7, and AND
25 62-8. By enabling these AND circuits, the value of the
increment in the normalizing circuit is passed through
directly to the register 62-10. This value is in turn
carried over line 68 to the adder where it is combined
with the previous beam position as determined by the
30 horizontal storage register 56-2. The increments are
continually added for the vector until such time as the
counter has counted to 0. In order to establish the con¬
dition of the electron beam, it is necessary to look at the
input signals to AND 76-12. For the vector operation, a
35 1 signal will be applied at the V output terminal of
F/F3, The paint flip-flop F/F 6 will be in the Set condi-
dition and applying a 1 at the P output terminal. Since the
vector has not been completed, the beam control flip-flop
F/Fl will provide a 1 at the END output terminal. Since
40 all of the input signals to AND 76-12 are of the 1 state,
a 1 will be provided on line 104 to OR 80-2. Since no
conditions are available at this time to disable the input
signal on line 80-6, AND 80-3 will provide the beam
intensity enable on line 94 and the vector will be dis-
45 played. It can be seen that the value of the vector will
not be altered depending on the selection of normal or
expand mode. However it will be seen that the selection
of the expand mode will alter the location of the vector
by controlling the transmission from the horizontal stor-
50 age register 56-2 through the output gating circuit 70
to the horizontal output register 58-1.
It is apparent that various other combinations and
sequences of operations can be visualized, but it is be¬
lieved that the foregoing fully describes the capability
55 of the improved display system and clearly defines the
operability of the circuitry.
Having set forth the various purposes and objectives
of the invention, and having fully described an embodi¬
ment which achieves the various objectives and pur-
60 poses, it being understood that various modifications in
the implementation or operation will become apparent to
those skilled in the art without departing from the spirit
of the invention, what is intended to be protected by
Letters Patent is set forth in the appended claims.
65 I claim:
1. In a display system having a cathode ray tube with
a viewing screen and circuitry for controlling an electron
beam for displaying data on the screen, the improve¬
ment comprising:
70 means for controlling the electron beam for displaying
data on the screen of the cathode ray tube; and
display control means coupled to the cathode ray tube
for causing data to be displayed in a first display
mode in a first area on said screen and for selec-
75 tively causing data to be alternatively displayed in
3,497,760
19
said first display mode or in a second display mode
in a second area on said screen, said display control
means including an expansion control circuit means
for expanding the scale of said data in a selected
sector of said second area on said screen to said
second display mode without disturbing said first
display mode of said data, in said first area, said
expansion control circuit means including sector
selection means for selecting a particular sector of
said second area to be displayed in said second dis¬
play mode, electron beam blanking decoder means
coupled to said sector selector means for produc¬
ing a first detection signal when said electron beam
is caused to tend to move out of said selected ex¬
panded sector in said second area, and a second
detection signal when said electron beam is caused
to move within said selected expanded sector in
said second area, and blanking circuit means
coupled to said beam blanking decoder means for
blanking said electron beam in response to said
first detection signal and for unblanking said elec¬
tron beam in response to said second signal.
2. A display system as in claim 1 and further includ¬
ing normal selector means for selecting said first dis¬
play mode of data in said first area and said second area
on said screen.
3. A display system as in claim 1 further including:
signal receiving means for receiving and at least tem¬
porarily storing a character control signal represent¬
ing that character data is to be displayed in said
first area; and
override control means coupled to said signal receiv¬
ing means and said expansion control circuit means
for temporarily overriding said expansion control
circuit means to cause said first display mode when
said character control signal is reecived.
4. A display system as in claim 3 and including char¬
acter spacing means for automatically causing character
data to be spaced in predetermined increments on the
viewing screen.
5. A display as in claim 4 including character size
spacing control means for providing a specifically as¬
sociated predetermined fixed spacing increment for each
character size available.
6 . A display system as in claim 1 and further includ¬
ing:
detecting means coupled to said display control means
for producing an off-screen signal when the digital
beam position data tends to force said electron
beam out of said selected sector of said second
area;
beam blanking means coupled to said detecting means
for blanking said beam when said off-screen sig¬
nal occurs; and
arithmetic means coupled to said detection means for
causing the complement of said digital beam posi-
20
tion to be used for locating said beam, whereby the
blanked beam will follow an on-screen path.
7. A display system as in claim 1 further including:
detecting means coupled to said display means for
5 producing an off-screen signal when the digital beam
position data tends to force said electron beam out
of said selected sector of said second area;
receiving means for receiving tabular character sig¬
nals representing tabular characters are to be dis-
10 played with a character spacing that is not to be
expanded; and
blanking means coupled to said detecting means and
to said receiving means for blanking said electron
beam whenever said off-screen signal and said tabu-
15 lar character signals are present, said blanking means
including holding means for holding said electron
beam blanked until said tabular character signal is
removed even when said off-screen signal is re¬
moved, whereby tabular characters which begin out
20 of said selected sector are blanked and the blank¬
ing continues even though the tabular characters
continue into said selected sector.
8 . A display system as in claim 7 and further includ¬
ing:
25 first means coupled to said expansion control circuit
for producing an expansion signal when a particu¬
lar sector is selected; and
second means coupled to said first means and to said
receiving means for preventing expansion of spac-
30 ing between said tabular characters when said ex¬
pansion signal is present.
9. A display system as in claim 7 and further includ¬
ing:
random character signal receiving means for receiv-
35 ing signals representing that random characters are
to be displayed in said second display mode; and
means coupled to said detecting means and to said
random character signal receiving means for pro¬
ducing an electron beam blanking signal when said
40 off-screen signal is present, whereby random char¬
acters out of said selected sector are blanked.
References Cited
UNITED STATES PATENTS
45 2,543,719 2/1951 Clark _ 315—27
2,580,977 1/1952 Tourshou et al._315—27
2,849,609 8/1958 Casey_ 178—7.5
3,056,918 10/1962 Lindberg et al._315—19 X
3,119,949 1/1964 Greatbatch et al._178—7.5
50 3,432,873 4/1969 Eggert_315_22
RODNEY D. BENNETT, Jr., Primary Examiner
BRIAN L. RIBANDO, Assistant Examiner
55 U.S. Cl. X.R.
178—7.5; 315—22
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